The present invention relates to apparatus for repairing or restoring the surfaces of metallic workpieces, especially for restoring surfaces which surround through bores or blind bores in workpieces or parts consisting of iron or the like. More particularly, the invention relates to improvements in apparatus which employ welding tools for deposition of fillets on the surfaces to be restored prior to machining of such surfaces to the desired size and/or shape.
The surfaces surrounding the holes or bores for bolts, pins, screws or like fasteners which are inserted into large and heavy metallic workpieces (e.g., into certain components of heavy-duty agricultural machines or the like) are subjected to extensive wear as a result of corrosion, play of the fasteners therein, unbalanced mechanical stresses and/or other influences. As a rule, the wear upon a bolt, screw, pin, stud, post or an analogous fastener presents no problems because the damaged fastener is simply replaced with a new one. The problem is much more serious if the damaged part is the piece which is provided with a through bore or hole or with a blind bore for reception of the fastener. Heretofore known proposals to repair such parts include increasing the diameter of the bore so as to remove the material which is adjacent to the damaged portion or portions of the surface surrounding the bore and introducing into the enlarged bore a prefabricated sleeve-like insert which is welded to the damaged workpiece. The insert then constitutes a new bearing or anchoring means for the fastener. A drawback of such proposal is that the cost of repairing the workpiece which is formed with the bore is very high for a number of reasons. Thus, it is necessary to store a supply of prefabricated inserts, it is necessary to enlarge the diameter of the bore by resorting to a first apparatus, and the insert must be welded to the workpiece by resorting to a discrete second apparatus or machine. Moreover, the welding operation invariably involves at least some deformation of the workpiece in the region of the enlarged bore. Still further, the material of the insert must be relatively soft because a hard or very hard insert is likely to become separated from the surrounding material of the workpiece upon completion of the welding operation. For example, an insert which is made of hardened iron is likely to become separated from a workpiece which also consists of iron. On the other hand, the utilization of relatively soft inserts entails pronounced wear thereon so that the useful life of a soft insert in a heavy-duty machine is very short.
The aforementioned copending patent application Ser. No. 472,038 discloses an apparatus which is designed to coat the damaged surface with a fillet of weldment and to thereupon machine the thus applied material so as to restore the dimensions of the bore in the metallic workpiece.